Parachute actuating mechanisms for military (and sport) applications have incredibly exacting requirements. They must be such as to release very large spring forces--needed to pull the rip cord--in response to very light actuating forces. They must be contained in a very small "package" or housing, as specified by the military and in order to minimize bulk and weight to thus aid the military or sport parachutist. They must be such as to open near a desired "set" altitude, the nearer the better. They must be so constructed that a preprinted altitude-indicating scale can be used, it being impractical in production to have all of the altitude settings on every dial for every parachute actuator specifically calibrated for that actuator.
There are many other severe requirements for parachute actuators, including (for example) the requirement that the actuator be able to be re-fired many times without deviating from its settings and operability. A further important consideration relates to manufacturing cost. One especially troublesome requirement has been what is called the drop test.
It is of late a military requirement that the actuator be able to be dropped three feet onto a two inch thick block of steel, without being broken or having its settings and characteristics changed. Attempts to meet this drop test, s especially or a reliable mechanism in a small package, have caused many problems in the industry. This is not to imply, however, that attempts to meet others of the above-stated requirements have not caused extremely severe problems.
In my co-pending patent application Ser. No. 96,679, filed Sept. 14, 1987, for a Parachute Release Apparatus (which is a continuation of application Ser. No. 770,401, filed Aug. 28, 1985), now Pat. No. 4,783,027, there is described a parachute-release apparatus of the type in which a timer is employed in conjunction with aneroid and other mechanisms, to cause opening of the parachute a predetermined number of seconds (or milliseconds) after the device drops through a pre-set altitude. The mechanism described in such patent application is believed by applicant to be highly satisfactory in all regards excepting those relating to the aneroid and the aneroid-compensating system. For example, the aneroid compensation means described in such application required that all aneroids in a given production batch be--in effect--brought down in performance to a "worst case" condition. Such worst case was that of the least-satisfactory aneroid in the batch. As another example, the aneroid described in such patent application had but a small amount of travel, and this necessitated extreme precision in associated parts and consequent problems vis-a-vis accuracy and repeatability, especially after the above-mentioned drop test was performed.
Referring now to a different aspect of parachute-release mechanisms and methods, it is common for the person using the parachute to pull a pin in order to arm the mechanism, and to insert the pin in order to cock the mechanism. This, while necessary in some applications, has problems in many others. For example, one problem relates to what the parachutist does with the pin after he or she pulls it. In actual life, the pins frequently become lost. Another problem is that the pulling of the pin leaves a hole in the mechanism, through which dust, dirt and grit can enter. The entrance of such foreign materials can interfere with future operations of the mechanism.
Referring next to another aspect of parachute-actuator mechanisms, there is one type in which the parachute does not open unless the parachutist is falling at a relatively high rate of speed. These mechanisms are employed on reserve chutes, since that it would be inconvenient and very likely disastrous for a reserve chute to open when the main chute has already been deployed. It has been difficult to achieve a highly reliable, yet relatively simple and economical, mechanism of this type.